Got a weird problem. When I start the truck it seems the electrical power goes up and down. Lights go bright and dim, fan motor up and down. When I rev it at or above 1000 rpm its seems ok. Dash voltage meter also up and down.

Batteries are pretty new. Cranks well when starting, even below 0. Could it be a faulty voltage regulator?

Truck is a 2007 2500 Megacab 4x4, automatic, 5.9, auto, 53,000 miles.

 

Maybe this is not a problem, nor is it weird. Have you considered that what you are seeing is the grid heaters cycling? They pull a lot of amps. The "problem" goes away once the engine warms up a bit.

Do a search here and you will find other references to this so-called "problem".

Check this out: https://www.dieseltruckresource.com/...d-start-57485/

 

grid heaters cycling

 

Thanks. This is the first Ram Diesel I've had, so I am unfamiliar with some of the things this truck does compared to others.

 

Typically the heater grid is enabled when the ambient intake temperature is below 65 F.